Blood Simple was a revelation for me when I saw it in a theater. It was scary and funny at the same time.
Ray is having an affair with his boss's wife (Abby). The boss (Marty) hires a private detective (Visser), to get proof of the affair. Ray and Abby prepare to run away together. Marty hires Visser to kill them.
Ray, a nice guy, winds up acting like a cold-blooded fiend. Marty, the vengeful husband, loses everything. Visser, a paid killer, ends up looking like a clown. Abby, a dependent woman, becomes the toughest of all.
Since everyone is keeping secrets, they sometimes work at cross-purposes. And accidents happen. Sometimes the surprises are scary, sometimes funny.
The filmmakers, Joel and Ethan Cohn, were certainly not the first to combine suspense and humor. Hitchcock always looked for humor in his stories and sometimes abandoned an idea if there was no humor in it. But the Cohn brothers made the scary parts scarier and the funny parts funnier.